Such a communication system is already known from the article "The QPSX Man" by R. M. Newman et al, published in IEEE Communications Magazine. April 1988, Vol. 26, No. 4, pp. 20-28. In this known system the signalling channels of each first cell are allocated to respective ones of a like number of priorities and each substation having data of a certain priority to be transmitted is able to write a data transmission request signal in the signalling channel allocated to this priority of a first cell. But since there is only a single such signalling channel per cell conflicts could occur and to avoid this each substation includes an additional receiver to assess the busy/free state of the concerned signalling channel of a received first cell before possibly writing a transmission request signal therein. Further, each substation is provided with means including an additional transmitter to monitor the use of the data channels of the second cells as a function of the request signals received in the signalling channels of the first cells. Both the additional receiver and the additional transmitter and the circuitry associated therewith have for effect that each substation is of relatively complex structure and therefore relatively expensive.
It should be noted that if the above known system processes data of a same priority the first cells only include a single signalling channel for transmitting request signals so that also in this case conflicts between the stations can occur and additional transmitters and receivers have to be provided.